This invention relates generally to medical instruments and, more particularly, to systems and methods for controlling the advancement of a guide wire through a body or a portion of the body, such as a blood vessel.
Guide wires are used during various interventional medical procedures to navigate therapeutic devices to a treatment site within a body, such as within a blood vessel. For example, to use a PTCA balloon device to clear an obstruction from a coronary artery, a guide wire is inserted into the femoral artery and advanced through the aorta to the obstruction in the coronary artery. The PTCA balloon device is then introduced over the wire and guided by the guide wire to the obstruction, where the balloon is then used to clear the obstruction.
However, advancing and steering guide wires through blood vessels is a difficult and risky procedure, even when practiced by skilled operators. Vessels are often tortuous or obstructed, or the tip of the guide wire itself is difficult to control. Thus, the use of guide wires typically entails the risk of puncturing or damaging the blood vessel, or else the guide wire simply fails because it is not rigid enough to penetrate certain barriers such as arterial plaque. A total occlusion of a blood vessel is an especially challenging barrier to successful use of a guide wire. Often, such occlusions are hardened by calcification and thus especially difficult to penetrate with a guide wire. When the tip of a guide wire is forced against such a hardened occlusion, the tip may be deflected toward the blood vessel wall, and, if advanced, may perforate the wall. To avoid such an undesirable outcome, the guide wire must be manually advanced by a skilled operator in carefully controlled increments. However, this is a difficult skill to acquire and even the most highly skilled operators risk damaging vessel walls. In addition, some calcified lesions present impenetrable barriers to the guide wire, even when operated by the most highly skilled operators.
A total occlusion of a blood vessel is an especially challenging barrier to successful use of a guide wire. Often, such occlusions are hardened by calcification and thus especially difficult to penetrate with a guide wire. When the tip of a guide wire is forced against such a hardened occlusion, the tip may be deflected toward the blood vessel wall, and, if advanced, may perforate the wall. To avoid such an undesirable outcome, the guide wire must be manually advanced by a skilled operator in carefully controlled increments. However, this is a difficult skill to acquire and even the most highly skilled operators risk damaging vessel walls. In addition, some calcified lesions present impenetrable barriers to the guide wire, even when operated by the most highly skilled operators.
Known guide wires include wires which range in diameter from 0.010 inches to 0.050 inches, and range in length from 2 feet to 10 feet. The distal tip of a typical known guide wire is shapeable into a curved or bent configuration and steered by turning the wire at the proximal end, thus transmitting torque through the wire to the distal tip. Known wires have varying degrees of rigidity (stiffness) which are selected according to the requirements of the particular procedure being performed. Softer, floppier wires are less likely to perforate vessel walls and are therefore better for navigating through tortuous arteries, but softer wires do not readily penetrate and cross occlusions. Stiffer wires are better for penetrating occlusions, but carry a greater risk of perforating or damaging vessel walls. Thus, an operator must trade off stiffness against a higher risk of perforation.
Other known guiding devices include catheters having a lumen for accommodating the movement of a guide wire. Such catheters are usually used in combination with a therapeutic device such as a PTCA balloon catheter. Known catheters also include exchange catheters, such as the Buchbinder catheter, which hold a position in the body while a wire extending through the catheter lumen is removed and replaced with a different wire. However, such catheters do not steer a guide wire through tortuous tissue, and do not provide incremental control of guide wire advancement to minimize risk of damage.
It would therefore be desirable to provide a catheter for controlling the advancement of a guide wire, wherein the catheter has a distal tip that can be deflected or steered so that the advancement of the guide wire inside a vessel can be more carefully controlled. It would also be desirable to provide such a catheter that controls the incremental forward movement of the guide wire distal tip. It would be further desirable to provide such a catheter coupled to an energy source to facilitate penetration of the catheter distal tip through difficult tissue such as total occlusions. It would be yet still further desirable to provide a catheter with a distal tip which can be stiffened as needed to penetrate occlusions, but which can also be allowed to soften to allow to facilitate steering through vessels.
These and other objects are attained by a catheter for controlling the advancement of a guide wire. In one embodiment the catheter includes a catheter body having a proximal end and a distal end, a first side lumen and a second side lumen, and a central lumen. A first control wire extends through the first side lumen, and a second control wire extends through the second side lumen. In one embodiment, the control wires each have a distal end that is coupled to the distal end of the catheter body. The catheter body includes a first, proximal portion and a second, distal portion. The distal portion is more flexible than the first portion so that the distal portion of the catheter body is flexible through a plurality of positions relative to the base portion. A control handle is coupled to the proximal end of the proximal catheter body portion. The control handle includes a control knob coupled to a deflection mechanism, which is coupled to the proximal ends of the control wires. The deflection mechanism translates movement of the control knob to motion of the control wires such that the wires move in opposing directions along the length of the catheter body. Thus, movement of the control knob produces opposing forces of the control wires on the distal portion of the catheter body, thereby causing the distal portion to flex relative to the first, proximal portion.
In an alternate embodiment, the first and second control wires are instead a first control portion and a second control portion of a single continuous control wire. An end of the single wire is introduced into the first side lumen at the proximal end, looped around at the distal end of the catheter body, and re-introduced into the catheter, into the second side lumen, terminating at the proximal end.
The present invention further includes a guide wire advancement mechanism in the control handle for controlling the advancement of a guide wire inserted through the catheter. The control handle knob is coupled to the advancement mechanism. The advancement mechanism includes a spring assembly in reversible engagement with a friction wheel. The guide wire passes through a guiding channel in a spring block in the spring assembly, so that the guide wire reversibly makes contact with the friction wheel. A geared drive wheel is coupled to the friction wheel. A first ratchet element coupled to a first spring element on the control handle housing reversibly engages the gear teeth on the drive wheel. xe2x80x9cClickingxe2x80x9d or brief pressure on the control knob engages the first spring element and first ratchet element so that the first ratchet element xe2x80x9cclicksxe2x80x9d forward one tooth on the geared drive wheel, thus rolling friction wheel forward. The guide wire making contact with the friction wheel is thus advanced incrementally forward. In one embodiment, a second ratchet element in engagement with a second geared drive wheel provides a brake against further advancement of the guide wire. In another aspect, the present invention is directed toward a catheter that navigates through difficult tissue by using an energy source to impart vibrational or rotating movement to tubing coupled to the catheter distal end. The energy source is coupled to the tubing by a PZT crystal, a rotating cam or a speedometer type cable.